Natural or synthetic rubber stabilized by an antioxidant extracted from fatty oils



NATURAL OR SYNTHETIC RUBBER STA BI- LIZED BY AN ANTIOXIDANT EXTRACTED 7 FROM FATTY OILS Loran 0. Buxton, Maplewood, N. J., ,assi gnor to Nopco Chemical Company, Harrison, N. J., a corporation of New Jersey No Drawing. Application December 27,1943,

Serial No. 515,796

' 10 Claims.

This invention relates to the stabilization of natural and artificial rubbers, and particularly to the stabilization of such rubbers against deterioration caused by oxygen and light.

2 ties of being substantially miscible with fatty oils at temperatures above room temperature and partially immiscible therewith at temperatures substantially below room temperature; experi- A wide variety of substances have heretofore 5 I ments in this connection have shown that $01", been added to natural and artificial rubbers for vents of this class may be used generally inthe v the purpose of stabilizing the same against detprocess herelnabove described. This process is rioration due to atmospheric oxygen and theacmore fully described and claimed in copending tion of light in combination with atmospheric application Serial No. 351,909, filed August 8, oxygen. Most of the substances proposed have 1940, now Patent No. 2,345,576. In accordance been rathercostly synthetic products, some of with this patent the following solvents may be which present definite toxicity hazards in the used; n-propyl alcohol, isopropyl alcohol, n-butyl handling thereof; Moreover, most of these analcohol. n-amyl e h lyi ny alcohol, tioxidants have left much to be desired in their ondary amyl alcohol, furfuryl alcohol, allyl alcoprotection of the rubber against oxidation, and hol. diaeetone o fly y ethyl tat particularly against oxidation stimulated by methyl formete, y mate, ethyl acetate, sunlight. Another shortcoming of antioxidants methyl acetate, isopropyl acetate, glycol diforheretofore proposed is their failure to prevent mate, glycol dleeetate. methyl levlllinaterethyl the phenomenon known as after-hardening in levulinate, methyl aceto acetate, ethyl aceto acesynthetic rubbers such as the butadiene and tate, methyl te, vinyl acet t f r chloroprene polymer rubbers. propionaldehyde,. crotonaldehyde, acetone,

In carrying out experiments relating to the t yl thyl k t n a t nyl acetone and p solvent extraction of fatty materials, it was disy ne ehlorehydl'int s also been ndt t covered that by' treating natural antioxidanthly p t t anti xidant t a ts y be containing fatty materials with certain types of tained from natural antioxidant-containing oilorganic solvents, highly potent extracts containb ing solids. e. g. oil-bearing Wh at rm meal, ing the majority of the natural antioxidants of 60m germ meal. Soybean meal, fish meals. et the fatty material concentrated therein may be y treating these materials with solvents by a obtained. Thus it has been found that a highly process similar to thatof appl n Serial N0- potent antioxidant extract maybe obtained from 351,909- T latte! P c is e y' a natural antioxidant-containing vegetable or scribed and claimed in eepending application fish oil by contacting said 011 with a suitable sol- S ri 7. filed ne 1941, n w a vent at room temperature or above, such that at n N 2,345,578! further information least the major portion of the oil is miscible with celning these Processes. re e y be h to the solvent, and then cooling the mixture to a as the above-identified p v temperature within the range of 0 C. to 70 C., o n y. it is an object of this invention whereby a solvent layer containing the desired to provide improved rubber'compositions which antioxidant extract separates. Among the solare C a ac e ed by bein h y resistant to oxvents which were found to be particularly sulti t v able for use in this proces are those listed in th 'Another object is to provide ch p r m s of r table below: stabilizing rubber compositions.

TABLE I Still another object is to provide antioxidants, v (1) Aliphatic and alicyclic monohydroxy alcoig andnke substances which hols containing from 3 to 6 carbon atoms. 2) Esters formed by the reaction of aliphatic gi lggg gg g is to protect natural gainst the concurrent action 101. and alicyclic alcohols with aliphatic monooxygen and light. I W carbwiylic acids Said esters cimtammg A still further object is to inhibit, the 'ff'afternot more than 8 carbon atoms hardening of synthetic rubbers such as butadi- (3) Aliphatic and alicyclic aldehydes containing ene and cmoroprene rubbers (4) i i: ,3 6 z g th Theforegoing and other objects. may be z z gg s con n ng not an achieved in accordance with this invention by the incorporation, into natural and artificial I It will be noted that these preferred solvents are rubbers, of one or more of the antioxidant all liquid organic compounds having the properconcentrates produced in accordance with the 3 aforesaid applications Serial Nos. 351,909 and 397,547. It has been found that natural and artificial rubber compositions containing modi-- cums of these antioxidants are efficiently protected against ordinary atmospheric oxidation. Compositions containing these antioxidants have further been found to be very successfully protected against the concurrert action of oxygen and light to a degree not attainable with any present commercial antioxidants of which the applicants are aware. Likewise, synthetic rubber compositions such as chloroprene and butadiene rubber compositions containing antioxidants as above set forth are'rendered free from the phenomenon of "after-hardening."

Any of the known natural or synthetic rubbers will be stabilized against oxidative deterioration by the incorporation of antioxidants as above set forth. Examples of specific types of rubbers which may be advantageously stabilized accord- 11 8 to this invention are natural hevea, balata, guttapercha, guayule and other biologically produced rubbers; and synthetic rubbers such as butadiene rubber, chloroprene rubber, butadieneisobutylene rubber, butadiene-styrene rubbers, and the like. In addition, the artificial rubbers are protected against the troublesome phenomenon known as after-hardening." The butadiene and chloroprene rubbers have hitherto been especially subject to this trouble, which is obviated in accordance with the present invention.

In the ractice of this invention, the antioxidants may be incorporated into the rubber to be stabilized at any stage during the compounding thereof, these antioxidants being readily compatible with all of these substances. The amount to be incorporated will, of course, vary in accordance with the nature of the particular rubber compound to be stabilized; the character of the fatty material from which the antioxidant was derived; the specific means employed for extracting the antioxidant: and the degree of antioxidant protection required in the application for which the rubber compound is designed. In general, proportions as low as 0.1%, based on the amount of rubber or artificial rubber in the compound, will impart a definite and practical degree of antioxidant protection to the final cured product produced therefrom. Ordinarily, about 0.5% to 1.0% of antioxidant, based upon the amount of rubber or artificial rubber, will be found most practical to use. The foregoing figures are naturally merely approximate and suggestive in view of the numerous variables involved in compounding rubber compositions and accordingly the exact amount of antioxidant to be employed is best determined by preliminary small scale experiment in each particular case, bearing in mind the foregoing general rules and the specific use for which the rubber composition is destined.

Instead of being incorporated into massive rubber compositions, the antioxidants may be dispersed into natural or artificial rubber latices and, when so dispersed, serve to inhibit oxidation of the constituents of the latex. In such stabilized latices, the antioxidant will, of course, be carried through to the finished rubber articles fabricated from the latices, and will serve to protect the articles from oxidation. 7

In practicing this invention. it is preferred to use antioxidant concentrates produced from either soybean oil, wheat germ oil, corn germ oil, cottonseed oil. corn oil, sesame oil, peanut oil, etc.,' or anymixture of these and similar oils, or

4 antioxidant fractions produced from oil-bearing wheat germ meal, com germ meal, soybean meal,

etc. It is to be understood, however, that similar antioxidant fractions prepared from any natural antioxidant-containing animal or vegetable oil or oil-bearing solid may be used.

Preparation of antioridant Parts Crude soyabean oil 66.5 Isopropanol (91%):

1st por i n 218 2d por 206 The soyabean oil and first portion of the isopropanol were mixed and agitated at 50 C. for 15 minutes. An atmosphere of nitrogen was maintained above the materials during this operation.

The oil-isopropanol mass was then chilled to 25 The cake and undecanted sludge were mixed and agitated with the second portion of isopropanol in an atmosphere of nitrogen at a temperature of 50 C. for 15 minutes. The mass was then chilled to 25 C. and kept at this temperature for 2% days. A sludge and a supernatant isopropanol extract layer formed, and the latter was decanted and filtered. The resultant filtrate was combined with the filtrate "A, and theisopropanol removed from the combined filtrate by low pressure distillation in a nitrogen atmosphere. The residue was used as an antioxidant in the practice of the invention as hereinafter detailed.

Tests conducted on antioxidants Parts Pale crepe rubber 100.00 Titaniurnoxide 6.00 Zinc oxide 5.00 Sulfur 2.25 Benzothiazyl disulfide 1.00 Tetramethyl thiuram disulfide 0.20 Antioxidant 0.25, 0.50, 1.00 or 2.00

Antioxidant prepared as above described.

' Hydroquinone mono-benzyl ether Substituted phenylene diamine:

N-p-tolyl-N'-p-toly1 suifonyl p phenylene diamine manufactured by Naugatuck Chemical Company for use as a rubber antioxidant.

15 cured in a. press at 40 pounds steam for 15 minutes. Samples oi each of the cured compounds were artificially aged and tested as follows:

I. Tensile and elongation tests:

A. Fresh sample aged for 10 hours in air at 80 pounds per sq. in. pressure and 127 C. Tensile strength and elongation at break determined on aged sample.

B. Fresh sample aged 4 days in oxygen bomb at 80 C. and 300 pounds oxygen pressure. Tensile strength and elongation at break determined on aged sample.

C. Fresh sample aged 7 days in an oven at 100 C. Tensile strength and elongation determined on aged sample.

II. Light-oxidation tests:

A fresh sample was exposedto air and ultraviolet light in the standard testing machine 'known as the Fadeometer for at 38 C.

the results of thetests are tabulated herewith:

100 hours it is obvious that their resistance to lightoxidation, as indicated by the tabulated Fadeometer tests, is of a far higher order than that of the other compounds. It will be noted further that, in general, the applicant's optimum results are in most cases attained with the use of relatively small proportions, usually 0.50 or 1.00 parts, oi antioxidant, with concomitant economy of materials and avoidance of upsetting the bal- The protection afforded in accordance with this invention is, on the average, more eflective than that obtained with conventional antioxidants against simple oxidation, not promoted by light, of rubber compositions. Furthermore, rubber compositions stabilized in accordance with tlfls TABLE II.Trnsn.'n AND ElLONGA'iION Tasrs V Antioxidant Antioxidant Pre- I v Acetone-Aniline Hydroquinone Substituted Di-o-tolyl Etb iene I Piil'ttsloi fii fi g g' Condensate Monobenzyl Ether Phenyiene Diamine Diamine Ageing Procedure 181x183! om- Tensile Eionga- Tensile El a- Tensile Elon a- Tensile Elon a- Tensile El n pound Strength, tion. Strength, $0 Strength, tion Strength, tion Strength, t on ib./ln. Per cent lbJln. Per cent lb./in. Per cent lb./in. Per cent lb./in. Per cent 8%.? 3'38 322 3'338 242 5833 238 a 8 550 685 520 Agem- 1.00 '4, 000 150 '4, 000 710 31295 690 31050 680 580 ;co. 2.00 3, 050 750 3, 780 710 3, 500 "700 650 700 3 600 720 0. 25 100 275 240 250 220 Y 185 210 I 160 275 A. Air at lb./in.', 0. 50 215 155 210 225 210 170 235 245 127, 10 hi 1. 00 110 270 180 215. 225 215 235 255 230 255 as as a: 32s as .235 5 2 720. 615 2, 980 610 9 2 9 9 o. 50 '1, 310 590 520 320 2,120 535 2,'450 605 2,820 025 da'ys 1.00 1,100 580 2,000 .545 '2, 740 580 1, 910 600 2, 780 585 2- 00 360 365 1, 670 540 2, 660 595 1, 970 585 '3, 160 595 0. 25 415 185 '410 175 470 450 170 195 165 C. All at 100 0., 7 0. 50 435 195 380 480 400 165 160 160 days 1. 00 380 460 175 410 135 440 165 320 205 2. 00 400 185 485 450 130 470 345 "215 TABLE IIL-Fnnrzounrna Tss'rs (100 Hotms, 38 C.) Antioxidant Antioxidant Pre Di-o-tolyl Ethylene Acetone-Aniline Hydroqumone Substituted Phenylene PM or 'fig g ggf Diamine Condensate Monobenzyl Ether Diamine Antioxidant In Com- Dis- 0 Dis- Dis Dis- Dispound colorcolor- Color, Appearcolor- Color, Appearcolor- Color Appcarcolor- Color Appearation g gg ation ance ation ance ation ance ation ance Rating Rating Rating Rating Rating "3 yclowuu "g tan, grazed brovsn, crazed '3 gen "a..- 1g brovgi, crazed. o w 3 light tan 8 brown, crazed." 10 do l0 .n idgi fi fuu 10 D8. 3 do 10 10 do 10 do 10 D0.

The optimum results attainable by the use of the several antioxidants against the several oxidizing conditions are indicated in Tables I! and III by asterisks for convenient comparison. It will be noted that the best tensile strengths obtained by the anti-oxidants used in accordance with this invention are in all cases of the same order as the best tensile strengths resulting from the use of the other antioxidants under the same conditions of oxidation. Moreover, the optimum elongations obtained with antioxidants according to this invention are in practically all cases significantly greater than the optimum elongations secured with other antioxidants. With regard to the resistance of the stabilized rubber compounds of this invention,

invention exhibit a much more eflective resistance to the simultaneous action of light and of atmospheric oxygen such as is encountered, for instance, in light-colored rubber goods such as white side-wall tires, unpigmented drug sundries, athletic equipment, and the like. Further, the compositions of this invention involving artificial rubbers have the unique property, not heretofore developed in this class of compositions, of being free from after-hardening efiects.

What is believed to be specifically novel and is desired to be secured by Letters Patent is:

1. A rubber composition stabilized against oxidation containing a substance selected from the group consisting of natural rubber, rubbery polymer of butadiene, and rubbery polymers of prepared by contacting a substance selected from the group consisting of crude vegetable and fish oils and vegetable and fish oil-bearing solids at a temperature above room temperature with a solvent selected from the group consisting of aliphatic and alieyclic monohydroxy alcohols containing from 3 to 6 carbon atoms, esters formed by the reaction of aliphatic and alicyclic alcohols with aliphatic monocarboxylic-acids, said esters containing not more than 8 carbon atoms, aliphatic and alicyclic aldehydes containing not more than 6 carbon atoms and aliphatic ketones containing not more than 6 carbon atoms, cooling the mass to a temperature within the range oi C. to --70 0., whereby layers are formed, separating the solvent layer from the insoluble residue and removing the extracted natural antioxidant f-rom the solvent.

2. A rubber composition stabilized against oxidation containing natural rubber and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting a substance selected rom the group consisting of crude vegetable and fish oils andvegetable and fish oil-bearing solids at a temperature above room temperature with a solvent selected from the group consisting of aliphatic and alicyclic monohydroxy alcohols containing from 3 to 6 carbon atoms, esters formed by the reaction of aliphatic and alicyclic alcohols with aliphatic monocarboxylic acids, said esters containing not more than 8 carbon atoms, aliphatic and alicyclic aldehydes containing not more than 6 carbon atoms and aliphatic ketones containing not more than 6 carbon atoms, cooling the mass to a temperature within the range of 0 C. to -70 0., whereby layers are formed, separating the solvent layer from the insoluble residue and removing the extracted natural antioxidant from the solvent.

3. A rubber composition stabilized against oxidation containing butadiene rubber and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting a substance selected from the group consisting of crude vegetable and fish oils and vegetable and fish oil-bearing solids at a temperature above room temperature with a solvent selected from the group consisting of aliphatic and alicyclic monohydroxy alcohols containing from 3 to 6 carbon atoms, esters formed by the reaction of aliphatic and alicyclic alcohols with aliphatic monocarboxylic acids, said esters containing not more than 8 carbon atoms, aliphatic and allcyclic aldehydes containing not more than 6 carbon atoms and aliphatic ketones containing not more than 6 carbon atoms, cooling the mass to a temperature within the range of 0 C. to 70 C., whereby layers are formed, separating the solvent layer from the insoluble residue and removing the extracted natural antioxidant from the solvent.

4. A rubber composition stabilized against oxidation containing chloroprene rubber and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting a substance selected from the group consisting of crude vegetable and fish oils and vegetable and fish oil-bearing solids at a temperature above room temperature with a solvent selected from the group consisting of aliphatic and alicyclic monohydroxy alcohols containing from 3 to 6 carbon atoms, esters formed by the re- 8 action of aliphatic and alicyclic alcohols with aliphatic monocarboxylic acids, said esters containing not more than 8 carbon atoms, aliphatic and alicyclic aldehydes containing not more than 6 carbon atoms and aliphatic ketones containing not more than 6 carbon atoms, cooling the mass to a temperature within the range of 0 C. to 70 0. whereby layer are formed, separating the solvent layer from the insoluble residue and removing the extracted natural antioxidant from the solvent.

5. A rubber composition stabilized against oxidation containing a substance selected from the group consisting of natural rubber, rubbery polymers of butadiene, and rubbery polymers of chloroprene, and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting a substance selected from the group consisting of crude vegetable and fish oils and vegetable and fish oil-bearing solids at-a temperature above room temperature with isopropanol, cooling the mass to a temperature within the range of 0 C. to 'l0 6., whereby layers are formed, separating the isopropanol layer from theinsoluble residue and removing the extracted natural antioxidant from the isopropanol.

6. A rubber composition stabilized against oxidation containing a substance selected from the group consisting of natural rubber, rubbery polymers of butadlene, and rubbery polymers of chloroprene, and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting crude soyabean oil at a temperature above room temperature with isopropanol, cooling the mass to a temperature within the range of 0 C. to -70 0., whereby layers are formed, separating the isopropanol layer from the insoluble residue and removing the extracted natural antioxidant from the isopropanol.

'I. A rubber composition stabilized against oxidation containing a substance selected from the group consisting of natural rubber, rubbery polymers of butadiene, and rubbery polymers of chloroprene, and oxidation inhibiting amounts of a phosphatide and of a natural anti-oxidantcontaining material prepared by contacting a substance selected from the group consisting of crude vegetable and fish oils and vegetable and fish oil-bearing solids at a temperature above room temperature with a solvent selected from the group consisting of aliphatic and alicyclic monohydroxy alcohols containing from 3 to 6 carbon atoms, esters formed by the reaction of aliphatic and alicyclic alcohols with aliphatic monocarboxylic acids, said esters containing not more than 8 carbon atoms, aliphatic and alicyclic aldehydes containing not more than 6 carbon atoms and aliphatic ketones containing not more than 6 carbon atoms, cooling the mass to a. temperature within the range of 0 C. to 70 0.. whereby layers are formed, separating the solvent layer from the insoluble residue and removing the extracted natural antioxidant from soluble residue and removing the extracted natural antioxidant from the isopropanol.

9. A rubber composition stabilized against oxidation containing butadiene rubber and an oxidation inhibiting amount of a natural antioxidant-containing material prepared by contacting crude soyabean oil at a temperature above room temperature with isopropanol, cooling the mass to a temperature within the range of 0 C. to 70 0., whereby layers are formed, separating the isopropanol layer from the insoluble residue and removing the extracted natural antioxidant from the isopropanol.

10. A rubber composition stabilized against oxidation containing chloroprene rubber and an oxidation inhibiting amount of a natural antioxidant-containing .material prepared by con- 15 Number tacting crude soyabean oil at a temperature uble residue and removing the extracted natural antioxidant from the isopropanol.

LORAN O. BUXTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Buxton Apr. 4, 1944 Musher Feb. 17, 1942 

